1. Field of the Invention
The present invention relates to humanized, chimeric and human alpha-fetoprotein (AFP) antibodies, particularly therapeutic and diagnostic conjugates of humanized, chimeric and human forms. In particular, the invention includes Immu31 antibodies and methods of treating hepatocellular carcinoma, germ cell tumors, and other AFP-producing tumors using humanized, chimeric and human antibody forms. The present invention also relates to antibody fusion proteins or fragments thereof comprising at least two Immu31 MAbs or fragments thereof or at least one Immu31 MAb or fragment thereof and at least one second MAb or fragment thereof, other than the Immu31 MAb or fragment thereof. The humanized, chimeric and human Immu31 MAbs, fragments thereof and antibody fusion proteins thereof, or fragments thereof, may be administered alone, conjugated to diagnostic and/or therapeutic agents, in combination with a therapeutic or diagnostic immunoconjugate, in combination with other naked antibodies, or with at least one therapeutic agent and/or diagnostic agent. The present invention further contemplates DNA sequences encoding humanized, chimeric and human Immu31 antibodies and fragments thereof, antibody fusion proteins and fragments thereof, vectors and host cells containing the DNA sequences, and methods of making the humanized, chimeric and human Immu31 antibodies.
2. Background
Monoclonal antibodies (MAbs) have wide diagnostic and therapeutic potentials in clinical practices against cancer. Early clinical trials revealed encouraging results using radiolabled MAbs for the diagnosis/detection (radioimmunodetection: RAID) and treatment (radioimmunotherapy: RAIT) of malignancies in cancer patients (Goldenberg et al., (1993) (Intl. J. Oncol. 3:5-11; Goldenberg et al., (1995) Immunol. Today 16:261-264; Goldenberg (1993) Am. J. Med. 94:297-312; Goldenberg (1991) Adv. Exp. Med. Biol., 303:107-117). Monoclonal antibodies play a central role in cancer immunotherapy, either in naked forms, or as conjugates to cytotoxic agents, such as radioisotopes, drugs, toxins, or prodrug-converting enzymes (Goldenberg et al., (1993) Immunol. Today, 14:5-7). These approaches are under active evaluation, with different levels of developmental and clinical successes. Naked MAbs potentially may achieve clinical responses by inducing a cytotoxic effect upon binding to cell surface proteins that are over-expressed on cancer cells. Studies have shown that these therapeutic effects were accomplished by controlling tumor growth via programmed cell death (apoptosis), or by the induction of anti-tumor immune responses (Cragg et al., (1999) Curr. Opin. Immunol., 11:541-547).
The majority of clinically interesting antibodies were raised in mice. The problem of immunogenicity of murine MAbs in humans has been the major obstacle preventing their clinical application, especially in cancer therapy where large doses and repeated administrations are required to achieve maximum efficacy. It has been demonstrated that significant human-anti-mouse antibody (HAMA) responses were detected in approximately 50% of patients after a single injection of murine MAb; greater than 90% of patients developed HAMA following two or three repeated injections (Sears et al., (1984) J. Biol. Response Med. 3:138-150; Reynolds et al., (1989) Int. J. Rad. Appl. Instrum. B, 16:121-125; Shawler et al. (1985) J. Immunol., 135:1530-1535; Jaffers et al., (1986) Transplantation, 41:572-578). In addition, the therapeutic effects of these murine MAbs in humans, if any, are further mitigated with their short serum half-lives and inabilities to recruit human effector cells, such as complement-fixing cytotoxic T cells. With the advent of molecular engineering, we can now genetically modify the structure of an antibody without affecting its antigen specificity to minimize or eliminate the HAMA responses and simultaneously enhance its immune effector functions. The processes are called chimerization and humanization. These modified MAbs have been shown to possess attributes essential for enhanced clinical utility, i.e., decreased immunogenicities, longer serum half-lives in human, and the ability to recruit effector functions.
Alpha-fetoprotein (AFP) is a serum protein normally found at significant levels only in fetal blood. In adult blood, increased alpha-fetoprotein levels are associated with liver regeneration and certain carcinomas, such as hepatocellular carcinoma, hepatoblastoma, and germ cell tumors. Hepatocellular carcinoma (HCC or malignant hepatoma) is one of the most common cancers in the world, especially in Asia, certain parts of Africa, and is increasing in incidence in the West, probably related to the increased frequency of heptatis infections. Accordingly, there remains a need to develop new methods and approaches to treating HCC and other such cancers.
The present invention relates to murine, chimeric, humanized and fully human anti-alpha-fetoprotein antibodies and fragments thereof, particularly monoclonal antibodies (MAbs), therapeutic and detection/diagnostic immunoconjugates, and fusion proteins comprising at least one anti-AFP antibody or fragment thereof. Also contemplated herein are methods of diagnosing/detecting or treating a cancer using humanized, chimeric and fully human anti-AFP antibodies. The humanized, chimeric and fully human anti-AFP antibodies and fragments thereof, and antibody fusion proteins and fragments thereof, may be administered alone, as a therapeutic and/or diagnostic/detection conjugate or in combination with a therapeutic immunoconjugate, with other naked antibodies, or with other therapeutic agents or as a diagnositic/detection conjugate.